What the law says about the perjury allegations against Jeff Sessions

— -- Following the revelation that Attorney General Jeff Sessions met with the Russian ambassador to the United States on two occasions in 2016 despite assertions during his confirmation hearing that he had no contact with the country, some lawmakers and oversight organizations around Washington have questioned whether he committed perjury.

During the hearing, Sessions was asked by Sen. Al Franken, D-Minnesota what he would do "if there is any evidence that anyone affiliated with the Trump campaign communicated with the Russian government in the course of this campaign."

"Sen. Franken, I'm not aware of any of those activities," said Sessions. "I have been called a surrogate at a time or two in that campaign and I did not have communications with the Russians and I'm unable to comment on it."

The assertion from the attorney general that he "did not have communications with the Russians" has been proven false, and that has been confirmed by the Justice Department, which noted that Sessions took the meeting with Ambassador Sergey Kislyak "as a senator and a member of the Armed Services Committee" and not as a representative of the Trump campaign.

What does perjury law say?

Perjury is defined by 18 U.S. Code § 1621 which states that a person "having taken an oath" may not "willfully" make statements "which he does not believe to be true."

An additional statute on false statements contained within 18 U.S. Code § 1001 prohibits a person from "falsify[ing], conceal[ing] or cover[ing] up" "a material fact" or "making any materially false, fictitious, or fraudulent statement or representation" "in any matter within the jurisdiction of the executive, legislative or judicial branch."

Is there a case against Sessions?

It would appear that any pursuit of Sessions for perjury would come down to whether he was "willful" in his misstatement.

James Goodnow, a lawyer and legal and political commentator, says that any prosecution of Sessions would come from the U.S. Attorney's Office for the District of Columbia, which falls under the purview of the Justice Department, meaning the office "would have to go after its own boss."

"That is a huge conflict, so you would likely need a special prosecutor step in," said Goodnow. On Wednesday, Sessions announced that he would recuse himself from any investigations into the presidential campaign.

Even with a special prosecutor, as far as a perjury case goes, George Washington University Law School professor and legal scholar Jonathan Turley says "there is no compelling case for perjury based on the facts that we currently have."

"Sessions could argue that he was responding perhaps inartfully that to the part of the question dealing with the campaign," said Turley.

"I don’t think you can assume on an intent [to mislead] on such a question," he added.

Goodnow says the case would make for a difficult conviction.

"Since the 1940s, there have only been six convictions under the [perjury] statutes, largely because of the 'willfulness' requirement," he said.

Without being able to know for sure whether Sessions was purposefully misleading the committee, a conviction would be unlikely, he added.

A notable perjury case

In a recent example of a successful perjury conviction, I. Lewis "Scooter" Libby, an adviser to former Vice President Dick Cheney, was found guilty of lying to investigators about his role in leaking the identity of undercover CIA agent Valerie Plame in 2007.

After Libby claimed that he couldn't have been the source of the leak, multiple people came forward to testify that they learned of Plame's identity from Libby prior to when Libby said he had first received the information. At trial, Libby claimed to have simply forgotten he actually learned about the identity from Cheney a month before he said he had.

Prosecutors claimed that Libby knew he was lying and invented details about the origin of the leak.

But Libby’s defense team said that making false statements was not enough to convict Libby of the charges against him.

"There’s no question he got some things wrong in the grand jury, no question," defense attorney Ted Wells said. "But you've got to ask, 'Did he engage in intentional lying?'"

At trial, with guidance from the case's judge to the jury that Libby had to know his statements were false when he made them in order for him to be convicted of perjury, Libby was convicted on counts including making false statements to authorities and perjury before a grand jury.

ABC News' Audrey Taylor and Mike Levine contributed to this report.